A clear understanding of both the differences and similarities between the host galaxies of the three main classes of powerful active galaxy – radio-quiet quasars (RQQs), radio-loud quasars (RLQs) and radio galaxies (RGs) – is vital in any attempt to unify or relate the various manifestations of the AGN phenomenon. The unification of RLQs and RGs via orientation effects requires that the hosts of the two types be derived from the same population of galaxies. Meanwhile, the correlation between radio power and host morphology in nearby AGN, with radio-quiet objects (Seyferts) occurring in disc systems and radio-loud sources in ellipticals, is generally assumed to persist at higher redshifts and nuclear luminosities. However, in both cases the evidence remains ambiguous and, moreover, many previous studies have been based on poorly selected samples.